1. Field of the Invention
The present invention relates to a coding device, a coding method, a decoding device, and a decoding method of image data and programs of the same.
2. Description of the Related Art
In recent years, for the purpose of handling image data digitally and at that time transmitting and storing information highly efficiently, coding devices and decoding devices based on the MPEG (Moving Picture Experts Group), H.264/AVC (Advanced Video Coding), and other coding systems utilizing the redundancy peculiar to image information and compressing data by a discrete cosine transform or other orthogonal transform and motion compensation are now spreading in use for both distribution of information at broadcast stations etc. and reception of the information at general homes.
The above coding method assigns picture types I, P, and B based on a GOP (Group Of Pictures) structure to the plurality of picture data forming moving picture image data, performs intra-coding for the I-picture data, and performs inter-coding for the P- and B-picture data.
In the above coding device, however, for example, at a flat image region in the picture data, a noise pattern known as “refreshing” (grain noise) occurs in the decoded image. This becomes perceived and results in a drop in the quality of the decoded image.